Combustor chambers of gas turbine engines receive their air supply from an air supply chamber separated from the combustor chamber by a bulkhead. Such gas turbine annular combustors are typically formed with liners on the sides and a bulkhead at the forward end. Fuel injectors are located within each of a plurality of openings in the bulkhead and arranged to inject fuel into the combustor for combustion therein. A deflector assembly closes the opening between the fuel injector and the bulkhead in a manner to deflect air flow therethrough in a desired manner. Such deflector is usually slideably mounted to the bulkhead in a radial direction with respect to the injector axis, and slideably accepts the fuel injector in the axial direction. This allows for a reasonable degree of misalignment between the injector and the bulkhead.
Flame existing immediately downstream of the injector radiates intensely toward the bulkhead in all areas.
Accordingly, a radiation shield is normally desirable immediately around the injector.
Annular plates have been formed on the deflector extending radially parallel to the bulkhead for the purpose of providing a radiation shield. These annular plates have been a chronic durability problem commonly experiencing burning distortion or cracking. These plates not only experience high temperatures but experience temperature differentials at different radial locations. Since the shields have been a single annular plate, a thermal fight is established between the hot outer rim and the cooler inner portion. The hot outer portion tries to expand as a function of its temperature but is constrained by the cool inner rim which expands to a lesser extent. This enforces a stress leading toward buckling and cracking of the material which is already operating at an extremely high temperature.
Since the material forming the annular plate must be fabricated into the annular shape and tolerate the high differential temperatures and concommitant stresses, the choice of materials is somewhat limited. For instance low ductility material such as ceramics and cast turbine alloys cannot conveniently be used.
It would be desirable to have a deflector heat shield which is not subject to the thermal fight of the current heat shields, which permits selection of materials more tolerant of high temperatures, and which can be reasonably cooled and easily fabricated.